[ticket/10790] Remove a (kind of) dead code section from submit_pm().

The type of $user->data['user_id'] is (almost) guranteed to be integer
since session::session_create() casts it to integer.
The type of $row['user_id'] is only an integer if the DB driver adjusts the
PHP type according to the DB type. This is only done by some of our
not-so-popular DB drivers and is not the case for MySQL.

As such this comparison is (almost) never true and a PM is also sent to the
author itself when it is sent to a group the author is also a member of.

Since this behaviour seems to have been accepted by the communty, the dead
code is removed and current behaviour is kept.

Also, checking this in the loop seems to be a rather bad idea.

Introduced by 78b1c4caaa17cc8760b685ad41c19f15f9d89b68.

PHPBB3-10790
[ticket/10908] Download files only up to max_upload_filesize if limit is 0

PHPBB3-10908
[ticket/10550] Sort not installed styles list in the styles section of the ACP.

PHPBB3-10550
[ticket/10908] Document that 0 filesize configuration means limited by PHP

PHPBB3-10908
[ticket/10611] Generate db_tools instance in acp_database module.

PHPBB3-10611
[ticket/10611] Use phpbb_db_tools::sql_list_tables() instead of get_tables().

get_tables() was deprecated by phpbb_db_tools::sql_list_tables()

This prevents unnecessarily loading functions_install.php

PHPBB3-10611
[ticket/10611] Filter out not existing database tables when making a backup.

Using $this->db_tools->sql_list_tables() as the first argument gives us table
names as array keys as a by-product which might be useful at some point.

PHPBB3-10611
[ticket/10162] Add test cases for top level domain names longer than 6 chars.

PHPBB3-10162
[ticket/10162] Increase maximum length of email address TLD from 6 to 63.

Increase maximum length of email address top level domains from 6 to 63.

PHPBB3-10162
Merge remote-tracking branch 'naderman/ticket/10908' into develop-olympus

* naderman/ticket/10908:
  [ticket/10908] Document that 0 filesize configuration means limited by PHP
  [ticket/10908] Download files only up to max_upload_filesize if limit is 0
Merge branch 'develop-olympus' into develop

* develop-olympus:
  [ticket/10908] Document that 0 filesize configuration means limited by PHP
  [ticket/10908] Download files only up to max_upload_filesize if limit is 0
[ticket/10751] Add sql_lower_text() to database abstraction layer.

On MSSQL, LOWER() can only be called on bounded strings (i.e. varchar or char).
So, in order to use it on a text column, we have to convert it to an
appropriate type. We do so using the SUBSTRING function.

PHPBB3-10751
[ticket/10751] Use sql_lower_text() in view_log(). log_data is a text column.

PHPBB3-10751
Merge remote-tracking branch 'github-bantu/ticket/10751' into develop-olympus

By Andreas Fischer
via Andreas Fischer
* github-bantu/ticket/10751:
  [ticket/10751] Use sql_lower_text() in view_log(). log_data is a text column.
  [ticket/10751] Add sql_lower_text() to database abstraction layer.
Merge branch 'develop-olympus' into develop

By Andreas Fischer
via Andreas Fischer (1) and Nils Adermann (1)
* develop-olympus:
  [ticket/10751] Use sql_lower_text() in view_log(). log_data is a text column.
  [ticket/10751] Add sql_lower_text() to database abstraction layer.

Conflicts:
	phpBB/includes/db/dbal.php
Merge remote-tracking branch 'github-bantu/ticket/10162' into develop-olympus

By Andreas Fischer
via Andreas Fischer
* github-bantu/ticket/10162:
  [ticket/10162] Increase maximum length of email address TLD from 6 to 63.
  [ticket/10162] Add test cases for top level domain names longer than 6 chars.
Merge branch 'develop-olympus' into develop

By Andreas Fischer
via Andreas Fischer (1) and Nils Adermann (1)
* develop-olympus:
  [ticket/10162] Increase maximum length of email address TLD from 6 to 63.
  [ticket/10162] Add test cases for top level domain names longer than 6 chars.
Merge remote-tracking branch 'github-bantu/ticket/10611' into develop-olympus

By Andreas Fischer
via Andreas Fischer
* github-bantu/ticket/10611:
  [ticket/10611] Filter out not existing database tables when making a backup.
  [ticket/10611] Use phpbb_db_tools::sql_list_tables() instead of get_tables().
  [ticket/10611] Generate db_tools instance in acp_database module.
Merge branch 'develop-olympus' into develop

By Andreas Fischer
via Andreas Fischer (1) and Nils Adermann (1)
* develop-olympus:
  [ticket/10611] Filter out not existing database tables when making a backup.
  [ticket/10611] Use phpbb_db_tools::sql_list_tables() instead of get_tables().
  [ticket/10611] Generate db_tools instance in acp_database module.
Merge remote-tracking branch 'github-bantu/ticket/10550' into develop-olympus

By Andreas Fischer
via Andreas Fischer
* github-bantu/ticket/10550:
  [ticket/10550] Sort not installed styles list in the styles section of the ACP.